The U.S. patent application, Ser. No. 06/355,517, Filing Date 03/08/82, discloses such a gas-blast puffer-type circuit-breaker wherein a dual-blast nozzle arrangement comprises a first nozzle being made of electrically conductive material, and a second nozzle being made of electrically insulating material.
A movable compression cylinder at least partly made of electrically insulating material is provided with a tube-shaped contact piece which has to carry mainly the continuous current of the circuit-breaker.
During a current interruption the arc current is conducted by a likewise nozzle shaped contact piece being mounted on a metal cylinder sliding inside of a gas pipe and current conductor. Said sliding metal cylinder is rigidly connected with electrically conducting parts of said compression cylinder.
As a particularity of that design appears that the inner width of said gas pipe and current conductor is comparatively rather narrow. Thus the expansion of the insulating nozzle is limited, and that of the exhaust, too.
Both features result in a certain limitation of the high-current interrupting capability which in principle is inherent to the dual-blast nozzle arrangement as described.
As a relief of the narrow cross-sectional area of the gas-pipe the connecting rods for the actuation of the movable structural parts have been arranged outside. However, this measure represents only a modest remedy.